Approach Aviation announced “a zinc-coated coupling spanner wrench and unique coupling gear socket” on April 12. “Together, these tools allow the coupling to be held in place (mounted on the alternator or free-standing) while the coupling gear slippage is checked with a calibrated 3/8” torque wrench (as specified in the engine maintenance manual),” the company said.
The coupling protects the engine from being damaged in the event of an alternator failure. However, “an out-of-tolerance or improperly installed coupling can lead to catastrophic engine failure,” the company said.
Approach Aviation also said that without having specialized tools, it was difficult for shops to inspect and diagnose coupling failures, leading to inaccurate assumptions that the alternator had failed.
The coupling on these engines shouldbe inspected every 500 hours or whenever the alternator is removed from the aircraft, according to Approach Aviation.
Alyssa J. Cobb
AOPA Senior Director of eMedia and Online Managing Editor
AOPA Senior Director of eMedia and Online Managing Editor Alyssa J. Cobb began working at AOPA in 2004, is a flight instructor, and loves flying her Cessna 170B with her husband and son. Alyssa is also co-host of AOPA Live This Week.